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I was playing in a virtual machine, changing permissions for wordpress folders/files copied to /var/www/html, when I ran into a new experience:

I am in a terminal at /var/www/html and I launch commands at /var/www/html/dev
Octal permissions for subfolders are 775, and for files 664, when I begin.
I do sudo chmod -R 755 dev and all subfolders/files become 755
Then, to revert, I do sudo chmod -R 664 dev and now all permissions/group/owner/datemodified become "unknown".

Is 664 not a valid permission? But files were 664 prior to my commands?
Since I am in a virtual machine I can just go back to a previous snapshot, so I don't need help per se, but I would like to understand what is going on.

Last edited by pastic on Fri Apr 21, 2017 3:30 am, edited 1 time in total.